Acrhimesh Texture Problem
I'm not sure if this is a bug (when stuff is added) or by design but this addon seems to expect Cycles as the default engine as the new objects get created with a cycles mat (perhaps ask on the github repo?). Notice the engine switches when you add a new archimesh object. The texture isn't disappearing, the engine just changes and Blender Internal and Cycles materials can't be used simultaneously or interchangeably .

Simply switch back the engine, delete the cycles material from the archimesh and add a new material and texture that.